Polycondensation of kraft-lignin toward value-added biomaterials: carbon aerogels

ABSTRACT

Carbon aerogels are versatile materials for value-added applications such as supercapacitors, insulation materials, and super absorbers. In this work, a way to produce carbon aerogels from kraft lignin which is an abundant waste product from the pulp and paper industry is presented. This was achieved by forming hydrogels of lignin and formaldehyde which were then subjected to solvent exchange and extraction with supercritical CO₂. The resulting aerogels were converted into carbon aerogels by means of pyrolysis. The characterization was performed by gas adsorption and scanning electron microscopy that showed highly porous carbon aerogels with a specific surface area up to almost 600 m² g⁻¹ which is relevant for technical applications.

KEYWORDS:

• Lignin-formaldehyde
• lignin polycondensation
• sol-gel polymerization
• carbon aerogels

Acknowledgments

The authors thank Dr. Sebastian Leitner for his preliminary work in the field of lignin-based aerogels. The assistance provided by DI Dr. Christoph Unterweger and Oliver Katzenberger during the carbonization experiments was greatly appreciated.

Disclosure statement

No potential conflict of interest was reported by the authors. The funding sponsors had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, and in the decision to publish the results.

Data availability statement

Data availability statement Data will be made available upon request to the corresponding author at [email protected]. https://www.wood-kplus.at/en.

Additional information

Funding

This work was carried out within the research project BioRest (Biopolymers from biogenic raw- and waste materials) which was funded by the European Regional Development Fund (EFRE) and the province of Upper Austria.

Notes on contributors

Gottfried Aufischer

Gottfried Aufischer is a PhD student at the Institute for Chemical Technology of Organic Materials at the Johannes Kepler University Linz working for Wood K plus – Competence Center for Wood Composites & Wood Chemistry. He carried out the preparative work dealing with the production of lignin-formaldehyde aerogels and is currently working on the topic of lignin depolymerization for generating UV absorbers and antioxidants.

Birgit Kamm

Birgit Kamm is a Key researcher at Wood Kplus, Austría and an Honorary Professor Biorefinery Technology and Biobased Products at the Brandenburg University of Technology, BTU Cottbus-Senftenberg. Her research is focused on commercially viable biobased platform chemicals and materials. She is currently working on understanding the structure–property relationships between renewably sourced biobased polymers, biobased polymer additives.

Christian Paulik

Christian Paulik is a Professor at the Johannes Kepler University Linz and Head of the Institute for Chemical Technology of Organic Materials with expertise in conventional and biobased plastics and biotechnology.